The present invention relates to an elastic or resilient shaft coupling, such as for a diesel engine drive mechanism.
Various flexible or resilient shaft couplings are known. One such coupling is disclosed in U.S. Pat. No. 4,708,514, Walter et al dated Nov. 24, 1987 and foreign British disclosure 2,164,726 Walter et al which correspond to each other and which belong to the assignee of the present invention.
An essential basis for the construction of a resilient shaft coupling of this type is the torque at rated load that has to be transmitted. A further important characteristic is the resilience that is required, in which connection a specific load capacity in the rubber material of the resilient annular assembly must be ensured. Taking into account the permissible shearing stress of rubber, the necessary shearing surface for a predetermined torque of a rated load can be ascertained. One of the main dimensions of such a resilient shaft coupling is also provided at the same time.
The demand for a desired resilience in the shaft coupling can be fulfilled with known properties of the rubber material that is used by calculating the necessary spring length of the rubber. A further characteristic regarding the main dimensions of the shaft coupling is thereby provided. With this type of procedure in regard to the determination of the rubber body, rotationally symmetrical rubber bodies are produced that have correspondingly larger dimensions for larger torques that are to be transmitted.
In the case of operational stresses on resilient shaft couplings of this type, the shaft coupling apart from the transmission of the mean driving torque, is also acted upon with a dynamic moment that can be attributed to the unavoidable torsional vibrations of the drive mechanism. As the dimensions of the rubber body increase, the ratio of thermal stressability to mechanical stressability becomes more and more disadvantageous. Regarding this, it should be noted that the specific mechanical load remains constant because of the dimensions calculated whereas in contrast, the temperatures in the core area of the rubber body rise sharply due to the poor heat conductivity of rubber when the rubber body is increasingly enlarged. With the measures for dissipating heat that have been customary up to now, a certain level of thermal stressability can be obtained; however, this level is not adequate in numerous applications. To this extent, the question of the obtainable thermal stressability comes more and more into the forefront when assessing the applicability of resilient shaft couplings.
It is therefore an object of the present invention to provide a resilient shaft coupling of the aforementioned general type that, at given mechanical properties, provides considerably greater thermal stressability, especially with rubber bodies having larger dimensions, to avoid unacceptably high heating in the core area of the rubber body.